The deployment of vaso-occlusive devices such as embolic coils in the vasculature of the human body has become a standard procedure for treating endovascular diseases such as aneurysm. These devices are particularly useful in treating areas where traditional surgical procedures are impossible or pose a great risk to the patient, for example, in the treatment of aneurysms in cranial blood vessels. The deployment of vaso-occlusive devices is often accomplished using a delivery catheter. A vaso-occlusive device, such as an embolic coil, is attached to the end of a delivery member which pushes the coil through the catheter and out of the distal end into the delivery site.
In the case of aneurysm, vaso-occlusive devices such as embolic coils act by occluding the flow of blood to a vessel. The reduction of blood flow to the aneurysm reduces the blood pressure in the area of the aneurysm and reduces the risk of a burst aneurysm. Furthermore, the insertion of the vaso-occlusive device may facilitate thrombus formation in or at the site of the aneurysm. For example, the vaso-occlusive device may act as a scaffold upon which thrombus formation is initiated. In the optimal situation, thrombus formation is followed by neointima formation and then fibrosis. As a result, the blood flow within the aneurysm may be permanently occluded and the risk of a burst aneurysm is greatly reduced. However, in a significant number of cases re-canalization occurs, whereby blood flow is re-established. The resumption of blood flow may lead to compaction of the vaso-occlusive device, an increase in the size of the aneurysm and ultimately increase the risk of a burst aneurysm.
Embolic coils have been developed that can assume different shapes to occupy the space of a particular blood vessel. In addition, the coil may have a coating in the form of a foam that increases the volume occupied by the coil and improves the degree of occlusion
The thrombogenic properties of a coil may also be increased by disposing a coating material about the coil. U.S. Pat. No. 5,690,671 discloses coating the coil with collagen to increase the thrombogenic response. In this case, however, the presence of collagen can induce a thrombolytic response rather than a thrombogenic response. In U.S. Pat. No. 5,980,550, a coil is described wherein an outer water-soluble material is placed over an inner thrombogenic material. The dissolution of the outer layer in the patient leads to the exposure of the inner layer. However, in this case, there is little control over the rate of dissolution of the outer layer and the thrombogenic material may be exposed before correct insertion of the device or it may not be exposed adequately. These patents and other references listed herein are incorporated hereinto by reference.
Art such as this have problems making them less than satisfactory for a variety of reasons. Therefore, a need remains for a vaso-occlusive device system that addresses such problems and promotes thrombogenicity and prevents re-canalization to a more favorable and consistent extent and with a longer term of success than vaso-occlusive devices and manufacturing methods available heretofore.